The present invention relates to electrical connectors and in particular to self-locking connector assemblies.
Self-locking electrical connectors are presently used in a multitude of industries and in particular in the aircraft industry as an alternative to safety wire connector locking. A number of self-locking electrical connector assemblies which do not require safety wire have been devised. Illustrative of such connector assemblies is the connector assembly shown in Johnson U.S. Pat. No. 3,808,580 which incorporates an annular surface with a plurality of grooves against which is pressed a clutch plate with a plurality of dimples extending therefrom. The clutch plate is pressed against the engagement surface utilizing a wave spring. The entire assembly is held in place with a retaining ring positioned in a cavity between the coupling nut and the shell of the connector.
While the above-described arrangement and others similar to it provide suitable self-locking coupling connector assemblies in many applications, it has been found that connector failures have occurred in high vibration environments after extended periods of time. These failures have been a result of several different factors. For example, in some connector assemblies, the wave spring presses against the back of a clutch plate which engages an annular engagement surface of a flange extending from the outside surface of the connector shell. As the nut is tightened onto the mating shell, the wave spring presses against the back of the clutch plate to press the clutch plate against the engagement surface to prevent rotation of the nut. Such devices rely on the continued resiliency of the wave spring to keep the clutch plate pressed against the engagement surface. However, because of the configuration and the placement of the wave spring, tightening of the nut caused axial deformation of the wave spring to a point that creates a permanent deformation resulting in a decrease in the resiliency in the spring. After multiple couplings and uncouplings of the connector assembly the wave spring becomes deformed to an extent that it cannot hold the clutch plate against the engagement surface with sufficient force to prevent rotation of the coupling nut relative to the connector shell in the high vibration environment.
Another problem which existed in some connector assemblies was the dislodgment of the retention ring which holds the coupling nut to the connector shell and retains the wave spring and clutch plate in place. Specifically, it was found that occasionally in high vibration environments the retaining ring would become dislodged from its retaining groove in the coupling nut thereby removing the back surface against which the wave spring pressed. This prevented the wave spring from pressing the clutch plate against the engagement surface. The result was a breaking of connector seals and shorting between various pin connectors due to conductive contaminations.
In order to solve the above-described problems and to provide a connector assembly wherein the wave spring applies a continuous, substantially constant force against the back of a clutch plate, the present invention provides a means of keeping a retention ring in the retention groove without becoming dislodged by vibration, and by providing a structure which limits axial movement of the coupling nut relative to the shell on which the coupling nut is mounted so that the wave spring is never compressed to a degree that will cause permanent deformation and hence a loss of resiliency.
In addition, the present invention provides an improved engagement mechanism between the clutch plate and the engagement surface whereby the engagement surface includes a ratchet face with a plurality of ratchet-like grooves which extend at a steep angle from the engagement surface on one side and at a shallow angle from the engagement surface on the other side so that the coupling nut can be more easily rotated to couple the connector shell to the mating shell than to decouple the connector shell from the mating shell.
Such an engagement mechanism prevents loosening of the coupling nut in a high vibration environment since it requires not only that the dimples in the clutch plate be moved against the force being applied by the wave spring but also requires that the coupling nut be simultaneously rotated. Furthermore, because of the multiple dimples and ratchet grooves about the entire circumference of the engagement and clutch plate surfaces, the entire clutch plate would have to move axially to effect disengagement. It would be insufficient for the clutch plate to twist slightly so that for example, only the dimples on one side of the clutch plate would become dislodged from the ratchet gooves.
The present invention also utilizes a plurality of shoulders which prevent the axial width of the space between the coupling nut and the shell in which the wave spring and clutch plate are retained to vary by more than a predefined amount. Therefore, the wave spring will retain its resiliency regardless of how much the coupling nut is tightened on the mating shell.